Processes for preparing chalcogenide alloys

ABSTRACT

A process for the preparation of chalcogenide alloys which comprises crystallizing a chalcogenide alloy, grinding and pelletizing the crystallized product, and evaporating the alloy on, for example, a supporting substrate to form a photoreceptor.

BACKGROUND OF THE INVENTION

The present invention relates to processes for preparing and controllingthe fractionation of chalcogenide alloys. More specifically, the presentinvention relates to processes for controlling the fractionation ofchalcogenide alloys during the vacuum deposition thereof. In oneembodiment, the present invention is directed to a process forcontrolling and suppressing the fractionation of chalcogenide alloys,and especially selenium alloys, which comprises the crystallizationincluding the partial crystallization of said alloy, grinding andforming pellets thereof, and subsequently vacuum evaporating therebyenabling, for example, desirable homogeneous products. Anotherembodiment of the present invention comprises the provision ofchalcogenide alloy pellets, the crystallization or partialcrystallization of said alloy pellets, grinding and forming secondpellets thereof, and subsequently vacuum evaporating. The productsresulting from the process of the present invention can be selected asphotoconductors in electrophotographic imaging systems, includingxerographic imaging and printing processes.

Chalcogens and chalcogenide alloys, and their use in electrophotographicprocesses is known. Generally, the aforementioned photoconductors areprepared by known vacuum deposition, flash evaporation, and chemicalvapor deposition methods. These methods possess disadvantages in someinstances. Thus, for example, with vacuum deposited chalcogenide alloysthe products obtained lack controllable reproducibility in theirhomogeneity thereby adversely affecting the electrophotographicelectrical characteristics thereof. As the components selected forvacuum deposition usually have different vapor pressures, suchcomponents tend to separate during the vacuum deposition process causingundesirable inhomogeneity, or fractionation thereof. Also, in the vacuumdeposition processes the components or species with, for example, highselenium content tend to evaporate more rapidly during the initialstages of deposition primarily, it is believed, because of their higherpartial vapor pressure, thus resulting in uncontrolled, undesirablefractionation. Accordingly, for example, the final photoconductor willcontain less selenium on the top surface, which adversely affects theelectrical characteristics thereof, and adds significantly to the costof the process. With the processes of the present invention, these andother disadvantages are avoided.

Electrophotographic photoconductive imaging members containing amorphousselenium can be modified to improve panchromatic response, increasespeed and to improve color copyability. These improved members areusually comprised of chalcogenide alloys such as alloys of selenium withtellurium and/or arsenic. The selenium imaging members may be fabricatedas single layer devices comprising a selenium-tellurium,selenium-arsenic, selenium antimony, or selenium-tellurium-arsenic alloylayer which functions as a charge generation and charge transportmedium. The selenium electrophotographic imaging members may alsocomprise multiple layers such as, for example, a selenium alloytransport layer and a continuous selenium alloy generator layer.

One known process for the preparation of photoconductors comprises thevacuum deposition of a selenium alloy on a supporting substrate such asaluminum. Tellurium can then be incorporated therein as an additiveprimarily for the purpose of enhancing the spectral sensitivity thereof.Also, arsenic can be incorporated as an additive for the primary purposeof improving wear characteristics, passivating against cystallizationand improving electrical properties of the resulting photoconductor.Generally, the tellurium addition can be accomplished as a thinselenium-tellurium alloy layer deposited over a selenium arsenic alloylayer to achieve the benefits of the photogeneration and transportcharacteristics of these respective layers. Fractionation ofchalcogenide alloys, such as tellurium and/or arsenic composition,during the vacuum evaporation processes results in an undesirableconcentration gradient in the deposited photoconductor. Accordingly,there results inhomogeneities (fractionation) in the stoichiometry ofthe vacuum deposited thin film alloys. More specifically, fractionationoccurs, it is believed, as a result of differences in the partial vaporpressure of the molecular species of the solid and liquid phases ofbinary, ternary and other multicomponent alloys. An important aspect inthe generation of chalcogenide alloy imaging members is controlling thefractionation of alloy components, one of the advantages of the processof the present invention, such as tellurium and/or arsenic during theevaporation of source alloys. More specifically, tellurium and/orarsenic fractionation control is particularly important since thetellurium and/or arsenic concentration at the extreme top surface of theresulting photoreceptor effects xerographic sensitivity, chargeacceptance, dark discharge, copy quality, photoreceptor wear, yield,crystallization resistance, and the like. For example, in single layerlow arsenic selenium alloy photoreceptors arsenic enrichment at the topsurface caused by fractionation can also cause severe reticulation ofthe evaporated film. Further, in single layer tellurium selenium alloyphotoreceptors, tellurium enrichment at the top surface due tofractionation can cause undue sensitivity enhancement, poor chargeacceptance and enhancement of dark discharge. Also, in two layer ormultilayer photoreceptors where low arsenic alloys may be incorporatedas a transport layer, arsenic enrichment at the interface with the layerabove can lead to residual cycle up problems. Moreover, in two layer ormultilayer photoreceptors where tellurium alloys may be incorporated asa generator layer, tellurium enrichment at the upper surface of thetellurium alloy layer can result in similar undue sensitivityenhancement, poor charge acceptance, and enhancement of dark discharge.

A specific method of preparing selenium alloys for evaporation comprisesthe grinding of amorphous selenium alloy shot (beads) and compressingthe ground material into pellet agglomerates, typically from about 150to about 300 milligrams in weight and having an average diameter ofabout 6 millimeters (6,000 micrometers). The pellets are then evaporatedfrom crucibles in a vacuum coater with a time/temperature crucibleprogram designed to minimize the fractionation of the alloy duringevaporation. One disadvantage of the aforementioned vacuum depositedphotoconductors, such as a selenium-tellurium alloy layer, is thecrystallization of the selenium-tellurium alloy at the surface of thelayer when exposed to heat. To retard premature crystallization andextend photoreceptor life, the addition of up to about 5 percent arsenicto the selenium-tellurium alloy can be beneficial without impairment ofxerographic performance.

Also, in deposited layers of selenium-tellurium alloys the amounts oftop surface tellurium present can cause excessively highphotosensitivity. This photosensitivity is variable and changes as thesurface of the layer wears away. Surface injection of corona depositedcharge and thermally enhanced bulk dark decay involving carriergeneration cause the toner images in the final copies to exhibit awashed out, low density appearance. Excessive dark decay causes loss ofhigh density in solid areas of toner images and a general loss of imagedensity. For example, when the photoreceptor comprises a single layerselenium arsenic alloy, about 1 to about 2.5 percent by weight arsenicbased on the weight of the entire layer at the surface of the alloylayer, there is provided protection against surface crystallization.When the concentration of arsenic is greater than about 2.5 percent byweight, electrical instability risks increase.

One known method for attempting to control fractionation is theselection of shutters for incorporation over the evaporation crucibles.The tellurium or arsenic rich material originating from the crucibledeposits on the shutter rather than on the photoreceptor substrate.However, in planetary coating systems, installation of shutters iscomplex, difficult and expensive. Further, after one or more coatings itmay be necessary to clean the surface of the shutters and the resultingdebris can cause defects to occur in subsequently formed photoreceptorlayers.

Accordingly, a problem encountered in the fabrication of chalcogenidealloy photoconductors, such as selenium alloy photoreceptors, is thefractionation or preferential evaporation of an alloy component wherebythe resulting film composition is not equivalent to the source alloy.Thus, the deposited film or layer does not have a uniform compositionextending from one surface to the other. For example, when tellurium isthe dopant, the tellurium concentration is high at the top surface andcan approach zero at the bottom surface in contact with the substrate ofthe vacuum deposited layer. This problem is also observed for alloys ofSe-Te, Se-As, Se-As-Te, Se-As-Te-Cl, or other halogens, mixturesthereof, and the like.

In copending U.S. application Ser. No. 946,238/86 now U.S. Pat. No.4,770,965, the disclosure of which is totally incorporated herein byreference, there is illustrated a process which includes heating analloy comprising selenium and from about 0.05 percent to about 2 percentby weight arsenic until from about 2 percent to about 90 percent byweight of the selenium in the alloy is crystallized, vacuum depositingthe alloy on a substrate to form a vitreous photoconductive insulatinglayer having a thickness of between about 100 micrometers and about 400micrometers containing between about 0.3 percent and about 2 percent byweight arsenic at the surface of the photoconductive insulating layerfacing away from the conductive substrate, and heating thephotoconductive insulating layer until only the selenium in the layeradjacent the substrate crystallizes to form a continuous substantiallyuniform crystalline layer having a thickness up to about one micrometer.A thin protective overcoating layer can be applied on thephotoconductive insulating layer. The selenium-arsenic alloy may bepartially crystallized by placing the selenium alloy in shot form in acrucible in a vacuum coater and heating to between about 93° C. (200°F.) and about 177° C. (350° F.) for between about 20 minutes and aboutone hour to increase crystallinity and avoid reticulation. Preferably,the selenium-arsenic alloy material in shot form is heated until fromabout 2 percent to about 90 percent by weight of the selenium in thealloy is crystallized. The selenium-arsenic alloy material shot may becrystallized completely prior to vacuum deposition. However, if desired,a completely amorphous alloy may be used as the starting material forvacuum deposition. In Examples II and V of this copending patentapplication, halogen doped selenium-arsenic alloy shot containing about0.35 percent by weight arsenic, about 11.5 parts per million by weightchlorine, and the remainder selenium, based on the total weight of thealloy, was heat aged at 121° C. (250° F.) for 1 hour in crucibles in avacuum coater to crystallize the selenium in the alloy. Aftercrystallization, the selenium alloy was evaporated from chrome coatedstainless steel crucibles at an evaporation temperature of between about204° C. (400° F.) and about 288° C. (550° F.).

In U.S. Pat. No. 4,780,386, the disclosure of which is totallyincorporated herein by reference, illustrates a process wherein thesurfaces of large particles of an alloy comprising selenium, telluriumand arsenic, the particles having an average particle size of at least300 micrometers and an average weight of less than about 1,000milligrams, are mechanically abraded while maintaining the substantialsurface integrity of the large particles to form between about 3 percentby weight to about 20 percent by weight dust particles of the alloybased on the total weight of the alloy prior to mechanical abrasion. Thealloy dust particles are substantially uniformly compacted around theouter periphery of the large particles of the alloy. The large particlesof the alloy may be beads of the alloy having an average particle sizeof between about 300 micrometers and about 3,000 micrometers or pelletshaving an average weight between about 50 milligrams and about 1,000milligrams, the pellets comprising compressed finely ground particles ofthe alloy having an average particle size of less than about 200micrometers prior to compression. In one embodiment, the processdisclosed in this patent comprises mechanically abrading the surfaces ofbeads of an alloy comprising selenium, tellurium and arsenic having anaverage particle size of between about 300 micrometers and about 3,000micrometers while maintaining the substantial surface integrity of thebeads to form a minor amount of dust particles of the alloy, grindingthe beads and the dust particles to form finely ground particles of thealloy, and compressing the ground particles into pellets having anaverage weight between about 50 milligrams and about 1,000 milligrams.In another embodiment of the '386 patent, mechanical abrasion of thesurface of the pellets after the pelletizing step may be substituted formechanical abrasion of the beads. The process includes providing beadsof an alloy comprising selenium, tellurium and arsenic having an averageparticle size of between about 300 micrometers and about 3,000micrometers, grinding the beads to form finely ground particles of thealloy having an average particle size of less than about 200micrometers, compressing the ground particles into pellets having anaverage weight between about 50 milligrams and about 1,000 milligrams,and mechanically abrading the surface of the pellets to form alloy dustparticles while maintaining the substantial surface integrity of thepellets. Pellets of the present invention can be formulated asillustrated in the '386 patent.

In copending U.S. application Ser. No. 179,375 now U.S. Pat. No.4,822,712, the disclosure of which is totally incorporated herein byreference, there is illustrated a process for controlling fractionation.More specifically, there is disclosed in this copending applicationprocesses for crystallizing particles of an alloy of selenium comprisingproviding particles of an alloy comprising amorphous selenium and analloying component selected from the group consisting of tellurium,arsenic, and mixtures thereof, said particles having an average size ofat least about 300 micrometers and an average weight of less than about1,000 milligrams, forming crystal nucleation sites on at least thesurface of said particles while maintaining the substantial integrity ofsaid particles, heating the particles to at least a first temperaturebetween about 50° C. and about 80° C. for at least about 30 minutes toform a thin, substantially continuous layer of crystalline material atthe surface of the particles while maintaining the core of seleniumalloy in said particles in an amorphous state, and rapidly heating saidparticles to at least a second temperature below the softeningtemperature of said particles, the second temperature being at least 20°C. higher than the first temperature and between about 85° C. and about130° C. to crystallize at least about 5 percent by weight of saidamorphous core of selenium alloy in the particles. With the process ofthe present invention, there is initially accomplished thecrystallization or partial crystallization as illustrated, for example,in the appropriate aforementioned copending application.

Further, in copending U.S. application Ser. No. 261,659 now U.S. Pat.No. 4,904,559 entitled Processes for Suppressing the Fractionation ofChalcogenide Alloys with the listed inventors Santokh S. Badesha, PaulCherin and Harvey J. Hewitt, the disclosure of which is totallyincorporated herein by reference, there is illustrated a process for thepreparation of chalcogenide alloy compositions which comprises providinga chalcogenide alloy; admixing therewith crystalline or amorphousselenium; and subsequently subjecting the resulting mixture toevaporation.

Also, in copending U.S. application Ser. No. 270,184 now U.S. Pat. No.4,894,307, the disclosure of which is totally incorporated herein byreference, there is described a process which comprises providing achalcogenide alloy source material, crystallizing said source material,vacuum evaporating the source material, and adding in effective amountsthereto, prior to, during, or subsequent to evaporation, organiccomponents such as siloxane polymers or greases, enabling the formationof a photoconductor with improved characteristics as illustrated herein.In one specific embodiment of the present invention, there is provided aprocess which comprises providing a chalcogenide alloy such as an alloycontaining selenium, including selenium arsenic and selenium telluriumalloys; crystallizing said alloy; and vacuum evaporating the alloy byheating at a temperature of from about 250° C. to about 350° C. in thepresence of an organic polymer such as a siloxane in an amount of fromabout 10 to about 30 parts per million, and depositing on a supportingsubstrate the desired chalcogenide alloy with reduced fractionation.Crystallization for the process of the present invention can beaccomplished as illustrated in the aforementioned copending application.

Of particular interest with respect to the invention of the presentapplication is copending U.S. application Ser. No. 07/179,193 filed Apr.8, 1988 now U.S. Pat. No. 4,859,411, entitled Control Of Selenium AlloyFractionation, the disclosure of which is totally incorporatyed hereinby reference, which describes and claims a process for crystallizingparticles of an alloy of selenium comprising providing pellets of analloy comprising amorphous selenium and an alloying component selectedfrom the group consisting of tellurium, arsenic, and mixtures thereof,said pellets having an average weight between about 50 milligrams andabout 1,000 milligrams, exposing said pellets to an ambient temperatureof between about 114° C. and about 190° C. until an exotherm occurs insaid pellets at between about 104° C. and about 180° C., carrying saidexotherm through to substantial completion, grinding said pellets intofresh powder having an average particle size of less than about 200micrometers, and compressing said fresh powder into fresh pellets havingan average weight between about 50 milligrams and about 1,000milligrams. With the present invention, in one important embodiment thecrystallized source alloy is initially subjected to grinding and thenpelletizing. A more complex process is, for example, disclosed in the'193 application since one has to initially prepare the pellets, andheat at higher deexotherm temperatures. On page 24 of the aforementionedapplication, it is indicated that suprisingly vacuum deposited layersformed directly from pellets that are heat treated by exposure totemperatures of between about 110° and 190° C. until an exotherm occursin the pellet at between about 104° and about 120° C. are characterizedby unaccepatably high photoreceptor sensitivity whereas vacuum depositedlayers formed from pellets subjected to the same heat treatment followedby grinding and repelletizing are characterized by photoreceptorsensitivity within the specified values. With the process of the presentinvention low crystallization temperatures are preferably selected, forexample, from about 85° to about 100° C., and preferably 95° C. therebyenabling an alloy product with a different microstructure, presumablysmaller crystallite size, which permits more desirable thermalproperties, including thermal conductivity, and superior heat transferfrom a alloy product particle to another alloy product particleproviding for superior control of fractionation.

Prior art U.S. patents mentioned in the Ser. No. 07/179,193 copendingapplication now U.S. Pat. No. 4,859,411 includes U.S. Pat. Nos.4,205,098; 4,609,605; 4,297,424; 4,554,230; 3,524,745; 4,710,442;4,583,608; 4,585,621; 4,632,849; 4,484,945; 4,414,179; 4,015,029;3,785,806 and 3,911,091. Also, as prior art there is mentioned SwissPatent Publication No. CH-656-486 published June 30, 1986; and JapanesePatent Publication Nos. J60172-346A and 57-91567.

There is illustrated in U.S. Pat. No. 4,513,031 a process for theformation of an alloy layer on the surface of a substrate, which forexample comprises forming in a vessel a molten bath comprising at leastone vaporizable alloy component having a higher vapor pressure than atleast one other vaporizable alloy component in the bath; forming a thinsubstantially inert liquid layer of an evaporation retarding film on theupper surface of the molten bath, the liquid layer of the evaporationretarding film having a lower or comparable vapor pressure than both thevaporizable alloying component having a higher vapor pressure and theother vaporizable alloying component; covaporizing at least a portion ofboth the vaporizable alloying component having a higher vapor pressureand the other vaporizable alloying component whereby the evaporationretarding film retards the initial evaporation of the vaporizablealloying component having a higher vapor pressure; and forming an alloylayer comprising both the vaporizable alloying component having a highervapor pressure and the other vaporizable alloying component on thesubstrate, see column 3, lines 33 to 54, for example. Examples ofvaporizable alloying components include selenium-sulfur and the like;and examples of vaporizable alloying components having relatively lowvapor pressures which include tellurium, arsenic, antimony, bismuth, andthe like are illustrated in column 4, reference for example lines 41 to50. Examples of suitable evaporation retarding film materials areoutlined in column 4, at line 54, and continuing onto column 5, line 36,such materials including long chain hydrocarbon oils, inert oils,greases or waxes at room temperature which readily flow at less than thetemperature of detectable deposition of the vaporizable alloyingcomponents having higher vapor pressures in the alloying mixture.Examples of retarding materials include lanolin, silicone oils such asdimethylpolysiloxane, branched or linear polyolefins such aspolypropylene wax and polyalpha olefin oils, and the like, see column 5.According to the teachings of this patent, optimum results are achievedwith high molecular weight long chain hydrocarbon oils and greasesgenerally refined by molecular distillation to have a low vapor pressureat the alloy deposition temperature, see column 5, lines 32 to 36. It isbelieved with the aforementioned process that the levels of organicswhich are incorporated into the resulting alloy film may be sufficientlyhigh causing negative adverse effects in the electrical properties ofthe resulting photoreceptor, for example, residual potential, darkdecay, charge trapping, and cyclic stability are adversely effected.These and other problems are avoided with the process of the presentinvention. Moreover, there is no teaching in this patent with respect toinitially crystallizing, or partially crystallizing the sourcecomponent, and thereafter vacuum evaporating this component in thepresence of a hydrocarbon, silicones, lanolins, which are a mixture ofpolyalcohols, polyesters, and fatty acids, especially the addition ofthese materials at low levels, that is from about 10 to about 30 partsper million thereby enabling photoreceptors with lower concentrations oforganic materials thus permitting the advantages of the presentinvention, and avoiding those disadvantages as illustrated in the priorart such as the '031 patent, including, it is believed, the ineffectivecontrol of fractionation when low levels of organic additives, such as,for example, from about 10 to about 30 parts per million are selected.

More specifically, there is described in the aforementioned U.S. Pat.No. 4,205,098 a process wherein a powdery material of selenium alone orat least with one additive is compacted under pressure to producetablets, the tablets being degassed by heating at an elevatedtemperature below the melting point of the metallic selenium andthereafter using the tablets as a source for vacuum deposition. Thetablets formed by compacting the powdery selenium under pressure may besintered at a temperature between about 100° C. and about 220° C.Typical examples of sintering conditions include 210° C. for betweenabout 20 minutes and about 1 hour, and about 1 to about 4 hours at 100°C. depending upon compression pressure. Additives mentioned include Te,As, Sb, Bi, Fe, Tl, S, I, F, Cl, Br, B, Ge, PbSe, CuO, Cd, Pb, BiCl₃,SbS₃, Bi₂ S₃, Zn, CdS, CdSeS and the like.

Furthermore, in U.S. Pat. No. 4,609,605, the disclosure of which istotally incorporated herein by reference, there is illustrated amultilayered electrophotographic imaging member wherein one of thelayers may comprise an amorphous selenium-tellurium-arsenic alloyprepared by grinding selenium-tellurium-arsenic alloy beads, with orwithout halogen doping, preparing pellets having an average diameter ofabout 6 millimeters from the ground material, and evaporating thepellets in crucibles in a vacuum coater; and in U.S. Pat. No. 4,297,424there is described a process for preparing a photoreceptor whereinselenium-tellurium-arsenic alloy shot is ground, formed into pellets andvacuum evaporated. Further, in U.S. Pat. No. 4,780,386 there isillustrated a process for the preparation of electrophotographic imagingmembers which comprises providing large particles of an alloy ofselenium, tellurium, arsenic, mechanically abrading the surfaces of thelarge particles whereby there is formed a certain amount of dustparticles based on the total weight of the alloy prior to abrasion,reference the Abstract of the Disclosure.

There is illustrated in U.S. Pat. No. 4,554,230 a method for fabricatinga photoreceptor wherein selenium-arsenic alloy beads are ground, formedinto pellets and vacuum evaporated. Also, the following U.S. Patents arementioned: U.S. Pat. No. 3,524,754 directed to a process for preparing aphotoreceptor wherein selenium-arsenic-antimony alloys are ground intofine particles and vacuum evaporated; U.S. Pat. No. 4,710,442 relatingto an arsenic-selenium photoreceptor wherein the concentration ofarsenic increases from the bottom surface to the top surface of thephotoreceptor such that the arsenic concentration is about 5 weightpercent at a depth of about 5 to 10 microns on the top surface of thephotoreceptor and is about 30 to 40 weight percent at the top surface ofthe photoreceptor, which photoreceptor can be prepared by heating amixture of selenium-arsenic alloys in a vacuum in a step-wise mannersuch that the alloys are consequentially deposited on the substrate toform a photoconductive film with an increasing concentration of arsenicfrom the substrate interface to the top surface of the photoreceptor. Inone specific embodiment, a mixture of three selenium-arsenic alloys aremaintained at an intermediate temperature in the range of from about100° to 130° C. for a period of time sufficient to dry the mixture; andU.S. Pat. No. 4,583,608 relating to the heat treatment of single crystalsuperalloy particles by using a heat treatment cycle during the initialstages of which incipient melting occurs within the particles beingtreated. During a subsequent step in the heat treatment process,substantial diffusion occurs in the particle. In a related embodiment,single crystal particles which have previously undergone incipientmelting during a heat treatment process are prepared by a heat treatmentprocess.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide processes for thepreparation of chalcogenide alloys.

Another object of the present invention is the provision of processesfor the preparation of chalcogenide alloys wherein fractionation isminimized or controlled.

Further, in another object of the present invention there are providedprocesses for the preparation of selenium alloys wherein fractionationof such alloys when evaporated is substantially avoided.

It is a further object of the present invention to provide an improvedprocess which controls arsenic and tellurium fractionation withinspecific ranges in selenium alloys thereof.

It is a further object of the present invention to provide an improvedprocess wherein prior to evaporation the chalcogenide alloy is subjectedto crystallizing, grinding and pelletizing.

Also, in a further object of the present invention there are providedprocesses wherein subsequent to crystallization at low temperatures thechalogenide alloy such as selenium arsenic, or selenium tellurium issubjected to grinding and pelletizing thereby controlling fractionation,and reducing the amount of, for example, arsenic at the top surface ofthe resulting photoreceptor to between about 0.5 and about 1 percent,and preferably 0.8 percent, when the selenium source alloy has anarsenic content of approximately 0.5 percent by weight; or reducing theamount of tellurium at the top surface of the photoreceptor to betweenabout 14.5 to about 17 weight percent tellurium, and preferably 15weight percent tellurium wherein the selenium source alloy has atellurium concentration of about 14.5 weight percent.

It is a further object of the present invention to provide an improvedprocess which increases photoreceptor yields.

It is a further object of the present invention to provide an improvedprocess which reduces the level of tellurium or arsenic fractionation.

Furthermore, it is another object of the present invention to provide animproved process which reduces the tellurium or arsenic distributionvariation throughout the thickness of a selenium-tellurium alloyphotoconductive layer.

Another object of the present invention is to provide an improvedprocess which controls the mechanical wear characteristics of thephotoreceptor surface.

Also, it is another object of the present invention to provide processeswhich limit the early loss of components containing higher (that ishigher concentrations than the starting source alloy, for example whenthe source alloy contains 90 weight percent of selenium, the seleniumcontent of the initial evaporated alloy product may contain 99 or 100weight percent of selenium) concentrations of selenium during theinitial stages of the evaporation process.

It is a further object of the present invention to provide processesthat provide evaporated films of selenium and its alloys with arsenicand/or tellurium which have, in many instances, superior photoconductiveproperties for extended time periods.

Another object of the present invention is to provide processes for thepreparation of photoreceptors which have controlled photosensitivitywithin narrow limits of for example+or -5 percent.

Also, it is a further object of the present invention to provide simpleprocesses that provide chalcogenide alloys since the grinding andpelletizing of crystallized materials produces less undesirable powder,and further the powder produced has less electrostatic charge permittingimproved pelletizing with reference to, for example, when amorphousmaterials are selected.

Moreover, a further object of the process of the present invention isthe formation of pellets subsequent to crystallization and grinding,which pellets are less subject to surface chemical reactions, that isfor example they are resisitant to humidity and heat, primarily sincethe pellets have been crystallized.

Another object of the present invention resides in the formation ofsmall particles subsequent to crystallization and grinding therebyproviding pellets which are dense and have improved thermal properties.

Further, in another object of the present invention there are providedprocesses wherein small, for example from about 8 to about 20,preferably about 10 microns particle diameter alloys, especiallyselenium alloy products with controlled or reduced fractionation result.

Additionally, in another object of the present invention there areprovided processes for the preparation of chalcogenide alloys whereinthe ground alloy prior to pelletizing has a narrow (more of one sizediameter) particle size distribution of particles different than whengrinding of amorphous shots is accomplished.

The above objects and other objects of the present invention areaccomplished by providing a process for preparing and controlling thefractionation of chalcogenide alloys. More specifically, the presentinvention is directed to a process which comprises providing achalcogenide alloy source material, such as a selenium alloy, includingthe specific alloys as illustrated in copending U.S. application Ser.No. 07/179,193, the disclosure of which is totally incorporated hereinby reference, crystallizing said source material; grinding thecrystallized product; pelletizing; and vacuum evaporating the sourcematerial enabling the formation of a photoconductor with improvedcharacteristics as illustrated herein. In one specific embodiment of thepresent invention, there is provided a process which comprises providinga chalcogenide alloy such as an alloy containing selenium, includingselenium arsenic and selenium tellurium alloys; crystallizing said alloypreferably at low temperatures, such as for example 85° to 100° C.;grinding the crystallized product; pelletizing; and thereafter vacuumevaporating the alloy by heating at a temperature of from about 250° C.to about 350° C. and depositing on a supporting substrate the resultingdesired chalcogenide alloy with reduced fractionation. In anotherspecific embodiment of the present invention, there is provided aprocess which comprises providing a chalcogenide alloy such as an alloycontaining selenium, including selenium arsenic, and selenium telluriumalloys; subjecting the aforesaid alloy to crystallization at atemperature of from about 85° to about 100° C., and preferably 95° C.;grinding the crystallized product; pelletizing; subjecting the resultingcomponents to evaporation by heating at a temperature of from about 250°C. to about 350° C. and depositing on a supporting substrate the desiredchalcogenide alloy with reduced fractionation, and containing from about0.3 to about 2 percent by weight of arsenic or tellurium and wherein theloss of the selenium rich component is avoided. Grinding and pelletizingcan be accomplished by known methods as illustrated, for example, inU.S. Pat. No. 4,780,386, the disclosure of which is totally incorporatedherein by reference, or by the process as illustrated in the appropriatecopending applications mentioned herein. In one embodiment of thepresent invention, subsequent to crystallization of the alloy beads of,for example, 0.5 to about 2, and preferably 1 millimeter diameter theyare added to a grinder such as a hammer mill grinder like the PaudelGrinder Model 2A, available from Fuji Industries of Japan, which grindsthe beads to a powder mixture wherein the average particle size diameteris from about 5 to about 50 microns, preferably from about 15 to about25 microns, and more preferably from about 8 to about 10 microns. Theaforementioned resulting powder particles usually have a narrow smallparticle size distribution, low electrostatic charge thereon, that issubstantially no clumping results as is the situation with amorphousselenium alloys. As a result, less grinding time, for example from about20 minutes, is needed and pelletization is simpler. Further, theresulting pellets are dense primarily because of the aforementionedsmall particle size. Pelletizing can be accomplished by well knownprocesses as indicated herein. In one embodiment of the presentinvention, pelletizing is effected by feeding the ground alloy powderinto a pelletizer, such as a Hata Pelletizer Model HPT-22A, availablefrom Hata Iron Works of Japan. Usually, the average diameter of theresulting pellets is from about 4 to about 10, and preferably from about5 to about 7 millimeters. The thickness of the pellets can varygenerally, however, they are from about 2 to about 6, and preferablyfrom about 3 to about 4 millimeters thick. Pellet weight is in oneembodiment from about 100 to about 1,000 and preferably from about 300to about 400 milligrams. Also, as the pellets are comprised of smallparticles with narrow particle size distribution the heat transfer fromone particle to another particle during the vacuum evaporation is veryefficient thus enabling in avoiding, or minimizing early undesirablelosses of selenium rich species thereby preventing or controllingfractionation.

In another specific embodiment of the present invention, there isinitially prepared the source alloy reactant product by known meltquenching methods. According to this method, the desired elements inappropriate amounts are mixed in a quartz vessel and are melted attemperatures of from about 400° to about 600° C. depending, for example,on the elements selected and other reaction parameters. Effective mixingis usually accomplished by purging the aforementioned molten mass with astream of a dry inert gas, such as nitrogen, argon, or mixtures thereof.Subsequent to heating and mixing the alloy components for an extendedperiod of time, for example, from about 2 to about 72 hours, the moltenmass resulting is shotted, for example, by pouring into cold waterthrough a screen. There results alloy shot, for example, an alloy shotof selenium-tellurium with about 70 to 80 percent by weight of selenium,and about 30 to 20 percent by weight of tellurium; or selenium arsenicwith about 95 to 99.8 percent by weight of selenium, and about 5 to 0.2percent by weight of arsenic. Also, the resulting diameter of the alloyshot is dependent on the screen size, and the shot is amorphous at thisstage as determined by X-Ray diffraction techniques (XRD). The exactcomposition of the alloy is usually determined by X-Ray FluorescenceSpectroscopy (XRF). Examples of shot produced in this manner includeselenium arsenic alloy with about 0.5 or 2 weight percent arseniccontent; SeTe alloys with 20, 12, 14.5, 25, or 30 weight percenttellurium; SeAsTe with Te, 8 weight percent, As, 2 weight percent, Te,10 weight percent, or As, 4 weight percent. Also, the diameter of theshots usually varies between about 0.5 millimeter to about 2.5millimeters. The resulting shot is then subjected to crystallization.Crystallization may be accomplished by a variety of means as indicatedherein, and detailed in the aforementioned copending applications. Forexample, in one embodiment with regard to a selenium tellurium alloycontaining about 10 weight percent of tellurium, and about 90 percent byweight of selenium, although other amounts, and other alloys may beselected as indicated herein, for example, the alloy shots are initiallyabraded, for example, in a Munson Abrader for about 1 hour to generatesurface nucleation sites. The abraded alloy is then added to open trays,for example metal or pyrex trays, and the trays are then placed into anoven. Subsequently, the oven temperature is increased to about 62° C.and the alloys maintained at this temperature for about 1 hour duringwhich time the trays are shaken periodically. Thereafter, thetemperature in the oven is increased to about 67° C. and maintained atthis temperature for about 1 hour. The trays are then shaken again, andthe temperature in the oven then further increased to about 75° C. andmaintained at this temperature for about 2 hours followed by increasingthe temperature in the oven to about 85° C., and maintaining thistemperature for about 1 hour. Subsequently, the temperature in the ovenis raised to about 100° C. and held at this temperature for about 8hours. During the aforesaid heating steps, the trays were periodicallyshaken by hand, usually an average of once every 30 minutes. Thereresults crystalline alloy shot as determined by XRD.

Thereafter, the resulting crystallized pelletized alloy source materialcan be added to crucibles in an 18 inch bell jar coater, which materialwas substantially evenly spread within the crucibles and coating on asubstrate such as aluminum accomplished in about 20 minutes. For thiscoating, which is known in the art, the crucible temperature is usuallymaintained at about 350° C., the vacuum was maintained at 4×10⁻⁵ Torr,the substrate temperature was maintained at 55° C., and the preferredaluminum substrate thickness was about 1 mil and generally up to about100 mils in thickness. There resulted a photoreceptor film with apreferred thickness of 50 microns as measured by a Permascope. Othersimilar process embodiments not specifically disclosed herein may beutilized providing the objectives of the present invention are achieved.

The aforementioned process embodiment is also applicable to thepreparation of other photoreceptors not specifically described herein,which photoreceptors, it is believed, possess the advantages illustratedherein. These photoreceptors can be comprised of known binary, ternary,and quaternary alloys including selenium arsenic, selenium tellurium,selenium antimony, selenium arsenic antimony, and the like, with orwithout halogen doping as illustrated herein, which alloys can beselected for the process of the present invention.

The substrate in a thickness of up to 100 mils, and preferably fromabout 1 to about 50 mils, selected for the deposited chalcogenideproduct may be opaque or substantially transparent and may comprisenumerous suitable materials having the desired mechanical properties.The entire substrate may comprise the same material such as anelectrically conductive surface or the electrically conductive surfacemay merely be a coating on the substrate. Typical electricallyconductive materials include, for example, aluminum, titanium, nickel,chromium, brass, stainless steel, copper, zinc, silver, tin, and thelike. Any suitable material such as nickel may be employed, whichconductive layer may vary in thickness depending on the desired use ofthe electrophotoconductive member. Accordingly, the conductive layer maybe of a thickness of from about 50 Angstroms to about 5,000 Angstroms.Generally, the substrate may be comprised of known materials includingorganic and inorganic materials. Examples of substrate materials includeinsulating nonconducting materials, such as various resins known forthis purpose, including polyesters, polycarbonates, polyamides,polyurethanes, and the like. The coated or uncoated substrate, which mayalso be comprised of conductive components as indicated herein, may beflexible or rigid and may have any number of configurations such as, forexample, a plate, a cylindrical drum, a scroll, an endless flexiblebelt, and the like. The outer surface of the supporting substratepreferably comprises a metal oxide such as aluminum oxide, nickel oxide,titanium oxide, and the like.

In some situations, intermediate adhesive layers between the substrateand subsequently applied layers may be desirable to improve adhesion.Preferably, these layers have a dry thickness between about 0.1micrometer to about 5 micrometers. Examples of adhesive layers includefilm-forming polymers such as polyester, polyvinylbutyral,polyvinylpyrrolidone, polycarbonate, polyurethane,polymethylmethacrylate, and the like, and mixtures thereof.

Any suitable photoconductive chalcogenide source alloy may be selectedfor the process of the present invention as indicated herein includingbinary, ternary, quaternary alloys, and the like, in effective amountsof, for example, from about 40 grams to about 55 grams when preparing a50 to 55 microns thick 4 inch by 6 inch alloy thin film to enable theformation of the vacuum deposited photoconductive layer. Preferredalloys include alloys of selenium with tellurium, arsenic, or telluriumand arsenic with or without a halogen dopant. Specific examples ofalloys of selenium selected for the process of the present invention areas indicated herein and include selenium-tellurium, selenium-arsenic,selenium-tellurium-arsenic, selenium-tellurium-chlorine,selenium-arsenic-chlorine, selenium-tellurium-arsenic-chlorine alloys,and the like. Generally, the selenium-tellurium alloy may comprisebetween about 5 percent by weight and about 40 percent by weighttellurium and a halogen selected from the group consisting of up toabout 70 parts per million by weight of chlorine and up to about 140parts per million by weight of iodine all based on the total weight ofthe alloy with the remainder being selenium. The selenium-arsenic alloymay, for example, comprise between about 0.01 percent by weight andabout 35 percent by weight arsenic and a halogen selected from the groupconsisting of up to about 200 parts per million by weight of chlorineand up to about 1,000 parts per million by weight of iodine all based onthe total weight of the alloy with the remainder being selenium. Theselenium-tellurium-arsenic alloy may comprise between about 5 percent byweight and about 40 percent by weight tellurium, between about 0.1percent by weight and about 5 percent by weight arsenic, and a halogenselected from the group consisting of up to about 200 parts per millionby weight of chlorine and up to about 1,000 parts per million by weightof iodine all based on the total weight of the alloy with the remainderbeing selenium. The expressions alloy of selenium and selenium alloy areintended to include halogen doped alloys as well as alloys not dopedwith halogen. The thickness of the aforementioned photoconductivechalcogenide alloy layer is generally between about 0.1 micrometer andabout 400 micrometers. Other thicknesses may be selected provided theobjectives of the present invention are achieved. Also, dopants mayinclude metals such as thallium, iron, manganese, and the like in placeof halogen. The aforementioned dopants are generally present in anamount of from about 10 to about 500 parts per million, and with halogenpreferably in an amount of 10 to 200, and preferably about 10 to about100 parts per million.

Crystallization or partial crystallization can be accomplished asillustrated herein and in the aforementioned copending applicationsespecially U.S. Ser. No. 179,375, the disclosure of which is totallyincorporated herein by reference. Vacuum evaporation involves asindicated herein, for example, heating from a crucible, the sourcecomponent, at a temperature of from about 250° C. to about 350° C.

Selenium-tellurium and selenium-tellurium-arsenic alloy photoconductivelayers are frequently employed as a charge generation layer incombination with a charge transport layer. The charge transport layer isusually positioned between a supporting substrate and the chargegenerating selenium alloy photoconductive layer. Generally, aselenium-tellurium alloy may comprise from about 60 percent by weight toabout 95 percent by weight selenium and from about 5 percent by weightto about 40 percent by weight tellurium based on the total weight of thealloy. The selenium-tellurium alloy may also comprise other componentssuch as less than about 35 percent by weight arsenic to minimizecrystallization of the selenium and less than about 1,000 parts permillion by weight halogen. In a more preferred embodiment, thephotoconductive charge generating selenium alloy layer comprises betweenabout 5 percent by weight and about 25 percent by weight tellurium,between about 0.1 percent by weight and about 4 percent by weightarsenic, and a halogen selected from the group consisting of up to about100 parts per million by weight of chlorine and up to about 300 partsper million by weight of iodine with the remainder being selenium.Elevated levels of arsenic in some applications, above about 4 percentby weight, can result in high dark decay, problems in cycling stability,and problems with reticulation of the photoreceptor surface. Theresistance of amorphous selenium photoreceptors to thermalcrystallization and surface wear begins to degrade as the concentrationof arsenic drops below about 1 percent by weight. As the chlorinecontent rises above about 70 parts per million by weight chlorine, thephotoreceptor begins to exhibit excessive dark decay.

Any suitable selenium alloy transport layer may be utilized in theaforementioned layered imaging member. Examples of these layers includepure selenium, selenium-arsenic alloys, selenium-arsenic-halogen alloys,selenium-halogen and the like. Preferably, the charge transport layercomprises a halogen doped selenium arsenic alloy. Generally, about 10parts by weight per million to about 200 parts by weight per million ofhalogen is present in a halogen doped selenium charge transport layer.When the halogen doped transport layer free of arsenic is utilized, thehalogen content should normally be less than about 20 parts by weightper million. Inclusion of high levels of halogen in a thick halogendoped selenium charge transport layer free of arsenic may causeexcessive dark decay. Imaging members containing high levels of halogenin a thick halogen doped selenium charge transport layer free of arsenicare described, for example, in U.S. Pat. Nos. 3,635,705 and 3,639,120,and Ricoh Japanese Patent Publication No. J5 61 42-537 published June 6,1981, the disclosures of which are totally incorporated herein byreference. Generally, halogen doped selenium arsenic alloy chargetransport layers comprise between about 99.5 percent by weight to about99.9 percent by weight selenium, about 0.1 percent to about 0.5 percentby weight arsenic, and between about 10 parts per million by weight toabout 200 parts per million by weight of halogen, the latter halogenconcentration being a nominal concentration. Halogen includes fluorine,chlorine, bromine, and iodine. Chlorine is preferred primarily becauseof its stability. Transport layers are described, for example, in U.S.Pat. Nos. 4,609,605 and 4,297,424, the disclosures of which are totallyincorporated herein by reference.

The first layer of multiple layered photoreceptors, such as a transportlayer, may be deposited by any suitable conventional technique, such asvacuum evaporation. Thus, a transport layer comprising a halogen dopedselenium-arsenic alloy comprising less than about 1 percent arsenic byweight may be evaporated by conventional vacuum coating devices to formthe desired thickness. The amount of alloy to be employed in theevaporation boats of the vacuum coater will depend on the specificcoater configuration and other process variables to achieve the desiredtransport layer thickness. Chamber pressure during evaporation may be onthe order of about 4×10⁻⁵ Torr. Evaporation is normally completed inabout 15 to 25 minutes with the molten alloy temperature ranging fromabout 250° C. to about 325° C. Other times and temperatures andpressures outside these ranges may be used as well understood by thoseskilled in the art. It is generally desirable that the substratetemperature be maintained in the range of from about 50° C. to about 70°C. during deposition of the transport layer. Additional details for thepreparation of transport layers are disclosed, for example, in U.S. Pat.No. 4,297,424.

The photoreceptors of the present invention can be selected for knownimaging and printing processes, reference for example U.S. Pat. Nos.4,265,990; 4,544,618; 4,560,635 and 4,298,672, the disclosures of eachof these patents being totally incorporated herein by reference. In someof these processes, latent images formed on the alloy photoreceptorproduct with the process of the present invention are developed,transferred to a suitable substrate such as paper, and fixed thereto by,for example, heating.

In another embodiment of the present invention, there is provided aprocess for the preparation of chalcogenide alloys which comprisesproviding a chalcogenide alloy source component, crystallizing thesource component, grinding the resulting product and evaporating thesource component. Further, in yet another embodiment of the presentinvention there is provided a process for controlling the fractionationof selenium alloys, which comprises providing a selenium alloy,crystallizing the alloy, grinding and pelletizing, and evaporating thealloy component.

The following examples are being submitted to further define variousspecies of the present invention. These examples are intended to beillustrative only and are not intended to limit the scope of the presentinvention. Also, parts and percentages are by weight unless otherwiseindicated.

EXAMPLE I

Amorphous selenium-tellurium (Se-Te), 12 weight percent of tellurium,and 88 weight percent of selenium alloy shots (100 pounds), wereprepared by mixing 88 pounds of high purity (99.999) selenium and 12pounds of high purity (99.999) tellurium in a quartz vessel. Thecontents of the vessel were then heated at 450° C. at which temperaturea molten mass resulted. The agitation of the molten mass wasaccomplished by sparging it with nitrogen gas. The sparging and heatingwere continued for 8 hours after which time the molten mass was pouredinto cold water (25° C.) through a stainless steel wire gauge. Theresulting product of alloy shots was collected and dried. These alloyshots were of an average diameter of about 2,500 microns as determinedby standard sieve analysis. An XRF (X-Ray Fluorescence) analysisindicated the composition to be comprised of a selenium-tellurium alloy(Se-Te), 12 percent by weight of tellurium and 88 percent by weight ofselenium. XRD (X-Ray diffraction) analysis indicated the above alloyshots to be amorphous. Fifty (50) grams of the above shots were loadedinto the crucibles of an 18 inch bell jar coater and a 50 micron alloyproduct thick film (88/12 Se-Te) was coated on an aluminum substrate,about 1 mil thick, by maintaining the crucible temperature of 350° C.,the substrate temperature at 55° C., and a vacuum of 4×10⁻⁵ Torr. Thealloy product film thickness of 50 microns was determined by Permascope.The EMPA (electron microprobe analysis) indicated that the averageconcentration of tellurium on the top 0.1 micron and 0.5 micron surfaceof the alloy film product was 36.9 percent and 33.2 percent,respectively. Also, EMPA analysis indicated that the distribution oftellurium concentration varied greatly from the top (36.9, 33.2) to thebottom (2.5, 1.1) of the alloy film product, thus indicating severefractionation.

EXAMPLE II

Twenty pounds of the amorphous selenium-tellurium, 12 weight percent oftellurium, 88 weight percent of selenium, amorphous alloy shots obtainedby the process of Example I was tumbled in a mechanical Munsen blender,Model MX-55 Mina Mixer available from Munson Machinery Company, forabout 0.5 to about 1 hour whereby selenium-tellurium alloy dustparticles having an average particle diameter of about 10 micronsresulted. The blender and subsequent steps are more specificallydescribed in U.S. Pat. No. 4,780,386, the disclosure of which is totallyincorporated herein by reference, see column 12, lines 1 to 24, forexample. Rotation of the cylinder in the blender caused the alloy beadsor shots to be moved upward by vanes until the beads tumbled downwardbecause of gravity. Less than about 20 percent of the selenium telluriumalloy beads were fractured. The resulting selenium tellurium alloy,88/12, was then ground into a powder having an average particle diameterof about 30 microns as determined by a Coulter Counter in a hammer millgrinder Paudel Grinder, Model 2A available from Fuji Industries, Japan,for about 20 minutes. Thereafter, the resulting ground alloy powder wascompressed into pellets in a Hata Pelletizer, Model HPT-22A availablefrom Hatta Iron Works, Japan, resulting in an average weight of theaforesaid alloy of 300 milligrams. The pellets were of a thickness ofabout 3 millimeters, and had a diameter of about 6 millimeters.

Fifty grams of the above formed pellets were then placed in twocrucibles of an 18 inch bell jar coater and a 50 microns thick filmalloy product, 88/12, selenium-tellurium alloy was then deposited on analuminum substrate of thickness of one (1) mil by repeating theprocedure of Example I. EMPA analysis indicated that the averageconcentration of tellurium on the top 0.1 micron and 0.5 micron of thevacuum above deposited selenium tellurium alloy film was 15.23 percentand 15.6 percent, respectively. Also, the EMPA analysis indicated thatthe alloy product film had inhomogeneous distribution of the telluriumthroughout the resulting alloy film product, and thus considerabletellurium fractionation.

EXAMPLE III

A. Fifty (50) pounds of the amorphous Se-Te (12 percent by weight of Te,and 90 percent by weight of selenium) alloy shots prepared by theprocess of Example I were fully crystallized by abraiding in a MunsonAbrader for 1 hour and heating by placing the resulting alloy shots intoopen metal trays, and the trays were heated in an oven under ambient airflow at 67° C. for 1 hour. Within this time, the surface of the shotsturned shiny. The temperature of the oven was then increased to 67° C.and the shots maintained at 67° C. for 30 minutes. The trays containingthese shots were shaken 3 times during this 30 minute period. Thetemperature was then raised to 75° C. and the shots maintained at 75° C.for 1 hour. The temperature was then increased to 85° C. for 1 hour,followed by increasing to 93° C. for 30 minutes. The temperature wasthen increased to 95° C. for 8 hours. XRD (X-ray diffraction) indicatedthat the resulting selenium-tellurium (88/12) alloy shots werecompletely crystalline. The crystallized product was then subjected togrinding and pelletizing by repeating the procedure as detailed inExample I.

B. Fifty (50) grams of the above crystalline ground, pelletized alloyshots were then loaded into a crucible of an 18 inch bell jar vacuumcoater. These shots were spread evenly on the bottom of the cruciblewith a spatula. An aluminum sheet, which was 1 mil thick, was used as asubstrate. A thin Se-Te (88/12) film was vacuum deposited on thesubstrate at 350° C. crucible temperature, 4×10⁻⁵ Torr pressure, and 55°C. substrate temperature. After the coating was completed, the thicknessof the selenium-tellurium (88/12) alloy film photoreceptor as determinedby Permascope was found to be 50 microns. EMPA (electron microprobeanalysis) indicated the average concentration of tellurium at the top0.1 and 0.5 micron of the alloy film product (90/10 Se-Te) to be 13.7percent and 13.6 percent, respectively. In addition, EMPA analysis alsoindicated that the alloy film product had a relatively homogeneousdistribution of tellurium throughout the film product, thusfractionation was minimized.

EXAMPLE IV

A. Forty (40) pounds of amorphous Se-Te alloy (12 percent by weight ofTe, and 90 percent by weight of selenium), alloy shots prepared by theprocess of Example III, were ground into a fine powder with an averageparticle size diameter of about 10 microns in a hammer mill followed byforming pellets with a thickness of 3 millimeters and a diameter of 6millimeters by repeating the procedure of Example II.

B. Fifty (50) grams of the above crystalline alloy pellets were thenloaded into a crucible of an 18 inch bell jar vacuum coater. These shotswere spread evenly on the bottom of the crucible with a spatula. Analuminum sheet, which was 1 mil thick, was used as a substrate. A thinSe-Te (88/12) film was vacuum deposited on the substrate at 350° C.crucible temperature, 4×10⁻⁵ Torr pressure, and 55° C. substratetemperature. After the coating was completed, the thickness of theselenium-tellurium (88/12) alloy film photoreceptor as determined byPermascope was found to be 50 microns. EMPA (electron microprobeanalysis) indicated the average concentration of tellurium at the top0.1 and 0.5 micron of the alloy film product (88/12 Se-Te) to be 12.4percent and 12.0 percent, respectively. In addition, EMPA analysisindicated that the alloy film product had a relatively homogeneousdistribution of tellurium throughout the film product, thusfractionation was eliminated.

With further respect to the present invention, although not usuallypreferred, alloy pellets may first be formed, followed bycrystallization, grinding, pelletizing and evaporating.

Although the invention has been described with reference to specificpreferred embodiments, it is not intended to be limited thereto, ratherthose skilled in the art will recognize that variations andmodifications may be made therein which are within the scope of thepresent invention and within the scope of the claims.

What is claimed is:
 1. A process for the preparation of chalcogenidealloys which comprises crystallizing a chalcogenide alloy sourcecomponent, grinding and pelletizing the crystallized alloy product; andevaporating.
 2. A process in accordance with claim 1 wherein thegrinding is accomplished by a hammer mill.
 3. A process in accordancewith claim 1 wherein the pelletizing is accomplished by a HataPelletizer.
 4. A process in accordance with claim 1 wherein the groundcrystalline alloy particles have an average diameter of from about 5 toabout 50 microns.
 5. A process in accordance with claim 1 wherein theground crystalline alloy particles have an average diameter of fromabout 8 to about 20 microns.
 6. A process in accordance with claim 1wherein the average diameter of the pellets formed is from about 4 toabout 10 millimeters.
 7. A process in accordance with claim 1 whereinthe average diameter of the pellets formed is from about 5 to about 7millimeters.
 8. A process in accordance with claim 1 wherein thethickness of the pellets formed is from about 2 to about 6 millimeters.9. A process in accordance with claim 1 wherein the thickness of thepellets formed is from about 3 to about 5 millimeters.
 10. A process inaccordance with claim 1 wherein the crystallization is accomplished at atemperature of from about 85° to about 100° C.
 11. A process inaccordance with claim 1 wherein there is deposited on a substratesubsequent to evaporation a chalcogenide alloy with reducedfractionation.
 12. A process in accordance with claim 1 wherein thereresults a selenium arsenic alloy with about 0.5 weight percent ofarsenic and about 99.5 weight percent of selenium.
 13. A process inaccordance with claim 1 wherein the source alloy is a ternary alloycomprised of selenium, tellurium, and arsenic.
 14. A process inaccordance with claim 1 wherein the alloy source component is partiallycrytallized.
 15. A process in accordance with claim 1 wherein vacuumevaporation is selected.
 16. A process in accordance with claim 1wherein the chalcogenide alloy contains selenium.
 17. A process inaccordance with claim 1 wherein the chalcogenide alloy contains seleniumwith tellurium, arsenic, bismuth, antimony, or mixtures thereof.
 18. Aprocess in accordance with claim 1 wherein the alloy is comprised ofselenium arsenic.
 19. A process in accordance with claim 1 whereinevaporation is accomplished at a temperature of from about 250° C. toabout 350° C.
 20. A process in accordance with claim 1 whereinsubsequent to evaporation there is deposited the alloy product on asubstrate.
 21. A process in accordance with claim 1 whereincrystallizing is accomplished at a temperature of 95° C.
 22. A processin accordance with claim 10 wherein there results a selenium arsenicalloy with from about 0.3 to about 2 percent by weight of arsenic.
 23. Aprocess in accordance with claim 10 wherein there results aselenium-tellurium alloy with from about 5 to about 40 percent by weightof tellurium.
 24. A process in accordance with claim 13 wherein thearsenic is present in an amount of 2 weight percent, the tellurium ispresent in an amount of 8 weight percent, and the selenium is present inan amount of 90 weight percent.
 25. A process in accordance with claim13 wherein the ternary alloy contains a halogen.
 26. A process inaccordance with claim 25 wherein the halogen is present in an amount offrom about 10 to about 200 parts per million by weight.
 27. A processfor the preparation of chalcogenide alloys which comprises providing achalcogenide alloy source component, crystallizing the source component,initially grinding and subsequently pelletizing the crystallizedproduct; and vacuum evaporating.
 28. A process in accordance with claim2 wherein there is deposited on a substrate subsequent to evaporation achalcogenide alloy with reduced fractionation.
 29. A process inaccordance with claim 27 wherein there results a selenium arsenic alloywith about 0.5 weight percent of arsenic and about 99.5 weight percentof selenium.
 30. A process in accordance with claim 27 wherein the alloyis partially crystallized.
 31. A process in accordance with claim 27wherein vacuum evaporation is selected.
 32. A process in accordance withclaim 27 wherein crystallizing is accomplished at a temperature of 95°C.
 33. A process for the preparation of chalcogenide alloys whichcomprises crystallizing a chalcogenide alloy component at a temperatureof from about 85° to about 100° C., grinding and pelletizing thecrystallized product; and vacuum evaporating.
 34. A process inaccordance with claim 33 wherein there results a selenium arsenic alloywith about 0.5 weight percent of arsenic and about 99.5 weight percentof selenium.
 35. A process in accordance with claim 33 wherein the alloyis partially crystallized.
 36. A process for controlling thefractionation of selenium alloys which comprises providing a seleniumalloy, crystallizing the alloy, grinding and pelletizing thecrystallized selenium alloy product; and evaporating the selenium alloy.37. A process in accordance with claim 36 wherein there results aselenium arsenic alloy with about 0.5 weight percent of arsenic andabout 99.5 weight percent of selenium.
 38. A process in accordance withclaim 36 wherein the alloy is partially crystallized.
 39. A process inaccordance with claim 28 wherein vacuum evaporation is selected.
 40. Aprocess in accordance with claim 34 wherein the selenium alloy is dopedwith a halogen.
 41. A process in accordance with claim 40 wherein thehalogen is present in an amount of form about 10 to 200 parts permillion.
 42. A process for controlling the fractionation of seleniumalloys comprising crystallizing a selenium alloy at a temperature offrom about 85° to about 100° C., grinding the alloy, pelletizing thealloy, and evaporating the alloy.
 43. A process in accordance with claim42 wherein grinding is accomplished by a hammer mill.
 44. A process inaccordance with claim 42 wherein pelletizing is accomplished by a Hattapellitizer.
 45. A process in accordance with claim 44 wherein thepellets formed are of a diameter of from about 4 to about 10millimeters.
 46. A process for the preparation of chalcogenide alloyswhich comprises providing a chalcogenide alloy source component,crystallizing the alloy at a temperature of from about 85° to about 100°C. grinding and thereafter pelletizing the alloy; and evaporating thealloy.
 47. A process in accordance with claim 46 wherein the alloy iscomprised of selenium-tellurium with about 12 weight percent oftellurium, and about 88 weight percent of selenium.
 48. A process inaccordance with claim 46 wherein a halogen is added to the alloy.
 49. Aprocess in accordance with claim 48 wherein the halogen is present in anamount of from about 10 to about 200 parts per million by weight.
 50. Aprocess in accordance with claim 48 wherein the halogen is chlorine. 51.A process for the preparation of chalcogenide alloys which comprisesproviding pellets of a chalcogenide alloy source component,crystallizing the source component, grinding and pelletizing thecrystallized product; and evaporating.
 52. A process for the preparationof chalcogenide alloys which comprises providing pellets of achalcogenide alloy source component, crystallizing the source component,initially grinding and subsequently pelletizing the crystallizedproduct; and vacuum evaporating.
 53. A process in accordance with claim52 wherein crystallizing is accomplished at a temperature of from about85° to about 100° C.
 54. A process for controlling the fractionation ofselenium alloys which comprises providing pellets of selenium alloy,crystallizing the alloy, grinding and pelletizing the crystallizedproduct; and evaporating the alloy.
 55. A process in accordance withclaim 54 wherein crystallizing is accomplished at a temperature of fromabout 85° to about 100° C.
 56. A process for the preparation ofchalcogenide alloys which comprise crystallizing a chalcogenide alloy,grinding the crystallized alloy, pelletizing the crystallized alloy, andevaporating.
 57. A process in accordance with claim 56 wherein thechalcogenide alloy contains selenium.
 58. A process in accordance withclaim 56 wherein the chalcogenide alloy is comprised of selenium with acomponent selected from the group consisting of tellurium, arsenic,antimony, bismuth, and mixtures thereof.
 59. A process in accordancewith claim 56 wherein the chalcogenide alloy is comprised of seleniumarsenic or selenium tellurium.
 60. A process in accordance with claim 56wherein the alloy is doped with halogen, or a metal.
 61. A process inaccordance with claim 56 wherein the dopant is present in an amount offrom about 10 to about 500 parts per million.
 62. A process inaccordance with claim 56 wherein fractionation is controlled.
 63. Aprocess in accordance with claim 56 wherein the crystallized alloy isvacuum evaporated.
 64. A process in accordance with claim 56 wherein thecrystallization is partial or complete.
 65. A process in accordance withclaim 56 wherein the crystallization is accomplished at a temperature offrom about 85° to about 100° C.
 66. A process in accordance with claim60 wherein the halogen dopant is present in an amount of from about 10to about 100 parts per million.
 67. A process for the preparation ofchalcogenide alloys which comprises crystallizing a chalcogenide alloy,grinding the alloy, pelletizing said alloy, and evaporating said alloy.68. A process for the preparation of chalcogenide alloys which comprisescrystallizing a chalcogenide alloy component at a temperature of 95° C.;grinding and pelletizing the crystallized product; and vacuumevaporating.
 69. A process for the preparation of chalcogenide alloyshots which comprises crystallizing a chalcogenide alloy shot sourcecomponent; grinding and pelletizing the crystallized alloy shot product;and evaporating.
 70. A process for the preparation of chalcogenide alloyshots which comprises providing a chalcogenide alloy shot sourcecomponent; crystallizing the source component; initially grinding andsubsequently pelletizing the crystallized product; and vacuumevaporating.
 71. A process for the preparation of chalcogenide alloyshots which comprises crystallizing a chalcogenide alloy shot componentat a temperature of from about 85° to about 100° C.; grinding andpelletizing the crystallized product; and vacuum evaporating.